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A. Field of the Invention
This invention relates generally to the art of man-machine interfaces; and, in particular, to keyboard interfaces which use one or both hands to signal chords of information to a computer.
B. Discussion of Related Art
Since the dawn of computers, people have been communicating with computers in many ways, but none so prolific as the standard QWERTY keyboard. The QWERTY keyboard was established more than 100 years ago in the golden age of mechanical engineering. Yet, while the mechanical design constraints of that golden era have long since passed away, the QWERTY keyboard has not - despite its many disadvantages. The layout of the QWERTY keyboard was designed to slow down an operator who might otherwise tax the response time of a mechanical assembly.
We are frequently amazed by the speed at which the fingers of an accomplished typist can fly over the QWERTY keyboard. Our amazement resides in the fact that we know that touch typing on a QWERTY keyboard is a highly complex skill requiring many many hours of practice to master, as well as continuous hours of practice to maintain. Yet, we also know that an alternative keyboard, which requires less time to master but which provides equal or superior performance, is certainly desired.
A chordic keyboard has been suggested as an alternative to the QWERTY keyboard. Compared to the QWERTY keyboard, a chordic keyboard is a keyboard with a limited number of keys. While the QWERTY keyboard requires a unique key for each letter, the chordic keyboard does not. Instead of assigning unique keys to each letter, a chordic keyboard may assign a chord of keys to each letter. Thus, the term "chordic keyboard" is derived from the fact that the operator may actuate several keys simultaneously to signal the letter of other symbol to the machine. The keys which are simultaneously activated are referred to as a "chord." In the domain of man-machine interfaces, each chord corresponds to a symbol from a symbol set. When the symbol set is the English language, each letter is defined as a symbol.
U.S. Pat. Nos. 4,360,892, 4,442,506 and 4,443,789, to Endfield et al. suggests a five key chordic keyboard wherein chord assignment is based on the pictorial relationship of the keys to letters and punctuation marks. In assigning chords based solely on pictorial relationships, the Endfield chordic keyboard ignores other relevant criteria, such as motor and perceptual determinants. These determinants were investigated and indexed by Ray, Kimchi and Gopher. (See "Perceptual and Motor Determinants of Efficient Data Entry," Proceedings of the Human Factors Society 31st Annual Meeting 1987 pages 820-829 hereinafter referred to as the "PM Determinant Paper").
U.S. Pat. No. 4,516,939 to Crimmins describes, among other matters, ten key device for receiving and translating chords made by an operator. However, Crimmins does not in any way address chord mapping schemes.
U.S. Pat. No. 4,833,446 to Eillam et al. describes a chordic keyboard wherein the chord assignment is based on groups of letters and wherein each group forms a recognizable combination of letters. These combinations are provided to assist the operator in associating the chord with the character. However, while such memory assisting associations may allow an operator to more easily learn chordic data entry skills, such memory assisted associations ultimately limit an operator's ability to achieve a performance level which is physiologically attainable.
Eilam et al.'s and Endfield et al.'s groupings are purely memory aids--aids which eventually inhibit ultimate performance.